Russell Wilson & David Seaman link up in Trafalgar Square

Manchester United's 2018-19 season began in the unlikely surroundings of Glendale, Ariz. as Jose Mourinho's side took on Club America of Mexico. A soporific game ended 1-1 and was only brightened up by young substitutes, one of whom coaches believe can be as good as -- if not better -- than Marcus Rashford.

"Did you enjoy that?" I asked Mason Greenwood as he walked through the mixed zone toward the United team bus. "Yeah!" he replied, smiling with childlike enthusiasm. Who could blame him, a 16-year-old living the dream of playing for one of the world's biggest clubs.

"Mason Greenwood has got the tools to go right to the top of the game and be a top player for United and England," says Danny Webber, who also came through the United system and is a regular watcher of the club's younger teams. "He's two-footed and can take set pieces with either foot. He's learning the centre-forward role properly now and he's scoring a lot of goals, but he needs to be challenged."

Greenwood, who celebrated his birthday on the first of this month, has played for the Under-18s and 19s in the UEFA Youth League this season, scoring in games vs. Berne and Valencia. He still has some way to go, but what is clear is that he looks far too good for his age group, where he has scored seven goals in his last four games.

"He went to an Under-20 tournament at the end of last season and won player of the tournament," Webber adds. "A player like him doesn't come along very often and you need to keep stimulating him and giving him challenges. He needs to keep his head down, keep the right attitude and work at his craft, but he's already got the stature. He's six foot; he's got a frame similar to Cristiano Ronaldo when he arrived at United. When Mason fills out that frame he's going to have even more power because at the moment he is doing it on ability."

Greenwood is one of the few young players from his club involved with England. Nobody from United was in the national team's Under-16 squad that trained at St Georges Park in August, while Manchester City had five players and Chelsea three. A recent 50-strong Under-15s camp featured only one from United; Tottenham had eight, Chelsea five and City four.

The Old Trafford youth system is still righting wrongs after several years of underinvestment, but the club have kept hold of Greenwood, despite numerous suitors that included Man City. He was recently given his first professional contract and the money involved is significant for him and his family.

Ben Thornley, an ex-United player who came through with the likes of David Beckham, Paul Scholes and Gary Neville and was tipped for a bright future before he suffered a serious knee injury, has watched Greenwood regularly.

"I love his energy and speed," Thornley says about Greenwood. "I love the fact that I don't know which foot he favours; combined with his speed that makes him a nightmare for defenders. He reminds me of Nicholas Anelka: fast, tall, slim, strong and can get a goal from nothing.

"Mason can be a top-class player if he keeps learning and listening, but he already has the size and temperament. He should soon go up to United's Under-23s, who need a centre-forward. They were relegated last season but they're doing well this season. He wouldn't be coming into a struggling side and he'd improve further against better players."

United will be patient but Greenwood is so highly rated that word within the club is that he is likely to work regularly with the first team after Christmas. Although, while a back-up to Romelu Lukaku is needed, it is unlikely to be the teenage prospect.

"Mason is a fantastic talent," says former United and Wales full-back Clayton Blackmore, who has coached Greenwood. "He played off the front in United's academy teams, who only play one up front in a 4-3-3 formation. Now he's a centre forward. He's two-footed, but he takes penalties and free kicks with his weaker foot and scores. It's very hard to take a free kick from your weaker foot from 25 yards."

Talented young players have come along before and the truth is that, while nearly every age group seems to have one and at the top clubs, most do not fulfil vast expectation. Little more than a decade ago, for example, Febian Brandy was winning player of the tournament as a 15-year-old and receiving bids for his talent from Barcelona. He ended up sleeping on a friend's couch and going unpaid in Greek football.

There are others: Federico Macheda looked hugely exciting at 17 when he was scoring vital winners for United's first team but, having recently joined Panathinakos is on the 10th club of his career at the age of 27. James Wilson's career was stalled by injury; he is on loan at Aberdeen having failed to feature under Mourinho.

Some young stars do continue to fly high -- the Busby Babes, the Class of '92 and, more recently, Gerard Pique, Paul Pogba and Giuseppe Rossi among them -- but they need luck to avoid the type of career-damaging injuries that afflicted Thornley and Wilson.

They also need a manager who trusts and plays them through the ups and the downs that affect almost every young player. Despite predictions to the contrary when he took charge, Mourinho has given chances to young players and certainly far more than his opposite number at Manchester City, Pep Guardiola.

But while a natural reaction from fans is to demand a player like Greenwood be given his opportunity, the timing has to be right and there are no more League Cup matches this season. Given his youth, though, he has plenty of time.